Mosquito Population Raises Zika Concerns

Concerns for the scope and reach of the Zika virus continue to grow as mosquito season nears the continental U.S. “Most of what we are learning is not reassuring,” Dr. Anne Schuchat, principal director of the Centers for Disease Control and Prevention, said in an April 11 press conference.

Schuchat said the Aedes aegypti mosquito, the carrier of the Zika virus, has been found in 30 states – more than double the 12 states where the species had been previously earlier. In an interview with the Dallas Observer, Dr. Christopher Perkins, Dallas County Health and Human Services medical director, said the focus of the county is to keep people and mosquitoes separate.

“The rationale is not only to keep people from being infected; it’s to keep people from infecting mosquitoes,” according to the Observer. Mosquito bites pass the virus both ways, Perkins told the Observer, meaning the A. aegypti species can act as a disease carrier between humans. Dallas County is advising limited outdoor activity at dawn and dusk, when the A. aegypti species is particularly active, according to the Observer. Wearing long, light-colored clothes, using insect repellent and draining standing water are also recommended.

According to Wired’s Sarah Zhang, the A. aegypti species likes to linger indoors, unlike most mosquitoes that bite humans. For this reason, Zhang said spraying neighborhoods will not kill them off, as was the case with the nocturnal West Nile mosquito.

To combat the spread of Zika locally, DCHHS began a radio campaign March 1 to educate the public, according to dallasnews. com. The county is using fabric bag traps that mimic a mosquitoe’s prey, Perkins said to the Observer. “The traps take in and release air like a mammal breathing, and is baited with a cocktail of chemicals that mimic the profile of human skin,” according to the Observer.

Canadian researchers of Ontario’s Laurentian University, led by Dr. Gerardo Ulibarri, an associate professor of medicinal chemistry and eco-health, developed an inexpensive, effective and non-toxic way to dramatically reduce mosquito populations, according to the BBC. Old tires are repurposed to serve as breeding traps called ovillantas, a device used to destroy the larvae of the A. aegypti species. “We are turning a weapon that mosquitoes use against us – old tires – against them,” Ulibarri told the BBC.

The device consists of two 20-inch pieces of tire, overlapped to create a mosquito-safe breeding environment, and a tube drain valve. The trap is filled with water and pieces of Pellon, a brand of lightweight utility fabric, or germinating paper to attract female mosquitoes who will lay their eggs inside.

Twice a week, the water is drained and the larvae filtered and destroyed. “It’s important to recycle the water because after the eggs hatch, they release pheromones into the water that tells other mosquitoes it’s a good, safe place to lay eggs,” Ulibarri told the BBC.

Initial tests of the ovillanta have been very effective, according to the BBC. In a 10-month study in Sayaxche, Guatemala, the researchers found that 84 ovillantas destroyed more than 18,000 larvae – seven times the amount of 84 standard traps – with no new cases of dengue fever reported during the time period.

Most adult victims who contract the virus will not experience any symptoms, which can include mild fever, skin rashes, muscle and joint pain and conjunctivitis, according to The Dallas Morning News.

The CDC also confirmed a correlation between the Zika virus and microcephaly, a condition that causes abnormally small heads in unborn infants during pregnancy. According to NPR, Dr. Arnaud Fontanet, a medical epidemiologist at the Pasteur Institute in Paris, conducted a study indicating a possible connection between Zika and Guillian-Barré syndrome, a condition that can cause temporary paralysis.

According to a small study by the American Academy of Neurology, Zika may also be a different associated with an autoimmune disorder that attacks the brain’s myelin, similar to multiple sclerosis.

The rate at which Zika can spread and how contagious the virus is have yet to be clearly defined.

Scientists at the Universidad Tecnologica de Pereira in Colombia estimated the contagious rate of Zika in the country in early April, according to Michaeleen Doucleff, a digital editor for NPR’s Science Desk. They calculated the reproduction number, or Ro – a mathematical term for the number of people who catch a disease from one sick person, on average, in an outbreak.

According to Doucleff, the scientists concluded that, in Colombia, Zika’s Ro was between three and six; meaning each person with the virus can spread it to about four others during the outbreak.

According to Doucleff, SARS and HIV have a Ro of about four. By comparison, the Ro of Ebola during the 2012 outbreak in West Africa was between 1.5 and 2.

As of press deadline, six cases of Zika had been confirmed in Dallas County. Five of the victims contracted the virus from a mosquito while traveling abroad and one from sexual transmission, according to
dallasnews.com.